Feeding mechanism for rock drills



Nov. 2, 1937. J. c. CURTIS I FEEDING MECHANISM FOR ROCK DRILLS Filed Nov. l2, 1934 3 Sheets-Sheet l ATTORN EY JOHN C. @UHT/S J. C. CURTIS FEEDING MEcHANIsM Fon ROCK DRILLs Nov. 2,` 1937.

3 Sheets-Sheet 2 Filed Nov. 12, 19.34

ATTRNEY J. C. URT|S FEEDING MECHANISM FOR RocKDRILLs Filed Nov. l2. 1934 3 Sheets-Sheet 3 INVENTOR ATTORNEY Nov. 2, 1937.

Patented Nov. 2, 1937 UNITED STATES tutti PATENT OFFQE FEEDING MECHANISM FOR ROCK DRILLS John C. Curtis, Garfield Heights, Ohio, assigner to The Cleveland Rock Drill Company, Cleve land, Ohio, a corporation of Ohio Application November 12, 1934, Serial No. 752,662

16 Claims.

"i improved and compact feeding mechanism for rock drills, wherein the overall length of the assembly is materially shorter than that of similarly actuated feeding mechanisms of equal feeding range.

Another object of this invention is to construct a fluid actuated feeding mechanism for rock drills in a manner whereby the movable parts ofthe mechanism are eiiiciently guided against lateral movement irrespective of their relative position,

eliminating thereby undue vibrations to be im parted thereto during the operation of the rock drill fed thereby. v

Another object of this invention is to provide a motive fluid actuated mechanism for rock drills with a device operable for controlling the pressure of the motive fluid actuating the former in either direction.

Another object of this invention is to produce a fluid actuated feeding mechanism for rock` drills of compact and sturdy construction, wherein lthe rock drill is adapted to travel at a greater rate of speed than that of the `feeding element.

Other objects and advantages reside in the specie construction and aggroupment of the elements peculiar to this structure as will become apparent from a more complete examination of this specification, wherein there are assembled and pointed out certain' combinations of parts and specific constructions indicative of the scope and spirit of the invention.

In the drawings:

Fig. l is a plan view of the drilling apparatus having the invention applied thereto.

Fig. 2 is a side elevational view of the drilling apparatus.

Fig. 3 is an enlarged longitudinal sectional Viewv taken in a plane indicated by line 3-3 in Fig. 6.

Fig. 4 is an enlarged cross sectional view taken in a plane indicated by line 5 4 in Fig. 2,

Fig. 5 is a cross sectional view taken in a plane indicated by line 5-5 in Fig. 4.

Fig. 6 is a cross sectional view taken in a indicated by line -G in Fig. 5.

Fig. '1 is an enlarged cross sectional view taken in a'plane indicated by line 1-1 in Fig. 2.

Figs. 8 to 16 inclusive are enlarged cross sectional views showing the throttle valve in different positions, Figs. 8, 9, l0 being taken in aplane indicated by line 8-8 in Fig. 5; Figs. 11, 12, 13 being taken in Va plane indicated by line ll`ll plane in the same figure; and Figs. 14, 15, and 16 being taken in a plane indicated by line Ill--M also in Fig. 5.

Fig. 17 is an enlarged longitudinal view of a portion of the throttle valve shown in Figs. 8 to 16.

Fig. 18 is an enlarged sectional View taken in a plane indicated by line I8-I8 in Fig. 2.

Referring to the drawings in which like symbols designate' corresponding parts throughout the several views, 20' designates a stationary shell or support being formed with aduality of longitudinally disposed slots or guideways 2l and 22y internally unitedY by a at surface 23 formed therebetween. Located in equidistant relation from the ends thereof, the stationary support 29' is formed with a cone 24 depending from the lower wall thereof, by which the support 29 may be affixed to a suitable mounting, such as a tripod or the like. Extending above the guideways 2l and 22, the left end portion in Fig. 2 of the support 2D is formed with longitudinal apertured lugs 25, each being formed with a counterbore 26 having secured therein a tube 21 with the face end wall thereofr mounted in abutting engagement with the bottom of the counterbore 26. The two tubes 21 extend toward the left in Fig. l to receive,vr in abutting engagement with the other end thereof, a cross plate 28, which is secured thereto by nuts 29 in screw tight engagement with the screw threaded end of a rod 30 located within each of the tubes 21, while the' other end of each rod extends through the apertured lugs respectively, to receive a nut 3l. By tightening the nuts 29 and 3|, it will be understood that the cross plate 28 and tubes 21 may be clamped rigidly to the support 20.

Slidable on the at surface 23 of the support 23, there is a feed tube 32 having guides 33 in slidable engagement within the gui-deways 2l and 22. The guides 33 are integral withthe feed tube 32 in longitudinal alignment therewith and extend substantially the full length thereof. The feed tube 32 is preferably made of a rectangular internal cross section, and has located therein a rectangular piston 34 comprising two pairs 35 and 36 of packings capable of fluid tight engagement with the inner wall of the tube, and two rubber buffers 31 and 38, the purpose of which will be explained later. The packings andbuffers are secured in clamped relation to the end of a stationary piston rod 39 by a nut 49. jacent the cone 24 of the support 20, the feed tube 32 has secured therein in fluid tight engagement with the inner wall thereof a Vertical plate 4|, which may be welded thereon through openings 42 formed through the upper and lower Walls of the feed tube at a place adjacent the plate 4|. The other end of the piston rod 39 extends through the cross plate 28 to which it is rigidly axed by a nut 44, preventing thereby the movement of the piston 34 relative to the support 20.

The other end of the feed tube 32 adjacent the cross plate 28 is closed by a head 45 having a rectangular projection 46 extending partway within the feed tube 32, and drilled to receive two bolts 41 transversally disposed through the tube 32, and adapted to receive cooperating nuts 48 by which the head 45 is secured to the feed tube 32. To assure a fluid tight joint between the projection 46 and the inner wall of the feed tube 32, there is aiixed to the end face of the former by screws 49 a packing member 50. lLocated in coaxial alignment with the rods 30 or tubes 21, the head 45 is formed with longitudinal apertured lugs 5| capable of slidable engagement with the tubes 21 extending therethrough, affording thereby guiding and supporting means for the head 45 and the end portion of the feed tube connected thereto. Located between the apertured lugs 5i the head 45 is provided with a longitudinally disposed bore 52, through vwhich the piston rod 39 passes. For a portion of its length, the bore 52 is enlargedrto form a counterbore 53 having, compressible thereinby a screw threaded plug 54, packing material constituting a stuffing box 55'assuring a fluid tight joint between the piston rod 39 and the internal wall of theV bore 52. Leading from the end of the rectangular portion 46 of the head 45 to a place adjacent the stuilng box 55, the bore 52 is also enlarged, thus providing a clearance 56 around the piston rod 39 extending through the packing member 50 into the rear end of the feed tube 32, the purpose of which will be explained later.

Located between one of the tubes 21 and the piston rod 39, the head 45 is provided with aY vertically disposed cylindrical boreY 51 formedY with a counterbore 58, the latter being terminated by a screw threaded portion adapted` to receive a plug 59. Slidably mounted within the bore 51, there is a valve 60 formed with a head 6| slidable within the counterbore 58. Both valve and head are provided with counterbores or internal chambers 62 and 63 leading from the ends thereof toward each other. The chamber 63 is properly machined to accommodate ar compression spring 64 having one end thereof seated on the bottom of the chamber 63, while the other end thereof is seated on the bottom of a similarly disposed counterbore formed within the plug 59. Similarly seated on the bottom ofV the valve counterbore 52, there is one end ofa compression spring 65, while the other end thereof is engaging the bottom of a counterbore formed within a cap 66 slidably mounted in the bore 51 between the valve 59 and the end of the bore throughrwhich the cap 66 free to pass. Starting from the end of the head 6| and leading'toward the small end of the valve 60, the latter is provided with an external annular groove 6'! which vis in constant communication with the interior of the head 6| or counterbore 63, through a restricted port 68. The portion of the cylindrical bore 51 within which the valve groove 61 isslidable, is equipped with an internal annular groove 69, whileA the counterbore 58 is provided with asimilarV groove 16 formed adjacentthe bottom of the counterbore 58 'with which the annular :shoulder 12 of the valve 69 is capable of abutting engagement.

2",o'?,5ei ,Y l

The outer annular edge of the valve shoulder 12 is povided with a duality of angularly disposed small' V-shaped grooves 13. Leading into the internal annular groove 10, the head 45 is provided with a screw threaded bore 14 to which may be connected the end of a pressure fluid conveying conduit. Provided through the cap 66, there is a restricted port 1|, the purpose of which Will be explained later. Y

Disposed above the cylindrical valve bore 66 in transversal relation therewith, the head 45 is provided with a throttle valve chamber 15 having a throttle valve 16 rotatable therein formed with a taperedy shank 11 extending therefrom and adapted to receive a handle 18, which is secured thereon against rotation by a key 19, and against longitudinal movement by a nut 86. 'I'he handle 18 is formed with a partly circular flange disposed in eccentric relation with the shank 11 of the throttle valve 16, Ythe peripherial wall of said flange constituting a cam 8| capable of engagement with the cap 66 slidable within the cylindrical bore 51. The throttle valve bore or chamber 15 is terminated by a screw threaded portion adapted to receive a plug 82 having mounted therein a locking mechanism 83 associated with the end face of the throttle valve 15 for locking the latter in any desired position. Centrally disposed Within the throttle valve 16, there is a port 84V in constant communication with the peripherial wall of the throttle valve through two restricted ports 85 and 86 located in la cross plane indicated by line |4.-|4 in Fig. 5. In the cross plane indicated byline in Fig. 5, the throttle valve 16 is provided with a semi-peripheral groove 81, and a radially disposed port 38 having a V-shaped groove 89 in constant communication therewith. In the cross plane indicated by line 8-8 in Fig. 5, the throttle valve 16 is provided with a groove90 and a radially disposed port 9| having aY V-shaped groove 92 Vopening therein. Thethrottle valve groove 81 is in constant communication with the groove through Va longitudinally disposed slot 93.

,I ieadingA from the annular groovef'69 formed within the Vvalve bore 51, `there is aport'43 .opening into` the throttle valve chamber 15 from where pressure iiuid'may be admitted into the central bore`84 of the throttle valve 16 through ports 94 provided within the locking mechanism 83. Opening into the throttlevalve chamber 15 at a place permitting its registration with the throttle valve port 85 or 86,' there is a restricted port 95 leading into the cylindrical bore 51 at a place adjacent the end of the valve 69. Formed within the head 45, there is a b-ore 96 having a counterbore adapted to receive one end of a small tube 91 having the other end thereof opening into the feed tube 32 at aplace adjacent the vertical end plate 4|. The bore 96 is connected with the throttle4 valve chamber 15 through a port 98, while the clearance 56 existing around the piston rod 39 within the head 45 is connected with the throttle valve chamber 15 through a port 99.

Located within the upper portion ofthe head Y45 there isY an enlarged chamber |00 in constant communication with. the throttle valve chamber 15 -through a portdl24. -'I'his chamber has the side thereof Vtoward 'the feed tube 32 open to permit the insertion of a sprocket wheel |0| therein, which is rotatably mounted on a vertical shaft |02 secured within the head 45 and extending centrally through the chamber |00. This last chamber is large enough to accommodate a chain |03 passing over the sprocket wheel |0| in operative engagement with the` teeth thereof. To one end of the chain |03 is aflixed a bolt |04 which is slidably mounted through an apertured lug |05 formed integral with the support 20 on one side of the feed tube 32. The bolt |04 is adapted to receive a nut |06 by which the bolt may be pulled through the apertured lug |05. In this manner, one braid or portion of the chain |03 is located on one side of the feed tube 32, while the other portion thereof Yextends over the feed tube and is affixed to a lug |01 depending from a fluid actuated rock drill or drilling motor |03. The upper wall of the feed tube 32 is provided with longitudinally disposed guideways |09 extending the full length thereof and adapted to receive in slidable engagement therewith corresponding guides ||0 integral with the drilling motor |08 which is thereby slidably guided on the upper face of the feed tube 32. The lug |01 depending from the drilling motor |08 is machined to about engage the upper wall of the feed tube 32 between the guideways |09. Surrounding tins lug and carried thereby, there is a yoke I i2 having attached to one end thereof the last mentioned end of the chain |03. Since the sprocket wheel |0| is disposed horizontally, the links of the chain |03 are disposed vertically relative to the feed tube 32. Secured to the other end of the yoke ||2 in longitudinal alignment therewith, there is. the last link of another chain H3 which extends therefrom between the guideways |99 over a sprocket wheel ||4 for operative engagement with the teeth thereof. This last sprocket wheel is rotatably mounted on a shaft ||5 transversally disposed through the feed tube 32 at a place adjacent the end thereof away from the head 45. After passing over the sprocket wheel 4, the chain I I3 extends under the-feed tube 32 and has that end thereof affixed tol support 20 as at Formed within the head 45 ahead of the chamber within which the valve 60 is slidably mounted, there is a screw threaded bore- ||1 adapted to receive a bolt ||8 formed with a head l| |9` having a handle |20 integral therewith. The bolt H8 extends through a plate |2| engageable with a step |22 formed on the head 45, and having an shown in Fig. 9, the valve cap 86is maintained partly out of the cylindrical bore 51 in engagement with the cam 8| by the action of the cornpression spring 95 on the cap 65. In this instance, the action of the spring 84 is calculated to be somewhat stronger than that ofthe spring 65, thus maintaining the valve shoulder 12- in abutting engagement with the bottom Vof the counterbore 58. The pressure fluid admitted into the groove 10 through the connection 14 is thereby prevented to flow into the supply groove 59, and consequently prevented to be admitted into the throttle valve 16 through therport 43. When the valve handle 18 is slowly rotated in either direction, the cam 8| engaging-the cap 38 will cause the inward movementvof the latter, compressing thereby the spring 55 which will cause the gradual movement of the valve 50 or of its shoulder 12 away from the bottom of the counterbore 58. The amount of the pressure uid iiowing from the groove 10 into the groove 69 may thus be regulated by the position of the valvev shoulder 12 relative to the groove 10. When the throttle handle is positioned at degrees from the positionshown in Fig. 9, the vhead 6| of the valve 60 is intended to fully uncover the groove 10, permitting thereby a free passage of the pressure uid from thegroove 10 into the groove 89 via the annular valve recess 61. When the valve handle 18 is positioned at only a small angle from the position shown in Fig. 9, the groove 10 is intended to be only slightly uncovered by the valve head 6|, causing thereby a restricted amount of the pressure fluid to be admitted into the groove 89 through the small V-shaped grooves 13. The

pressure admitted into the groove 59 via the valveexternal annular recess 61, is admitted into the valve head-6| through the restricted port 88, exerting pressure therein. That pressure together with the effort of the compression spring 84 willY tend to shift the valve in a closed position, that is, will tend to cause the engagement of the shoulder 12 with the bottom of the counterbore 58. By positioning the pressure controlling valve 60 ahead of the throttle valve 16, it will be understood that the amount of pressure fluid admitted into the latter from the groove 59 through the port 43, is first controlled by the valve 00.

Referring now to the throttle valve proper, it will be seen that when the latter is positioned as shown in Figs. 9, l2, and 15, a position which corresponds to vertical position of the valve handle 18, the ports 95, 98, and 99, are closed by the throttle valve. If some pressure fluid was to escape past the valve 60, which is in this instance maintained in a closed position, it would be arrested by the throttle valve 16.

During the rotation of the throttle valve 15in the direction of the arrow shown in Fig. 9, the port 9| thereof will register with the port 99 through the groove 92. In this instance, the action of the cam 8| on the cap 66 is not sufficient to cause the movement of the valve 50 in an open position, thus it will be understood that the throttle valve 16 is moved in an open position relative to the port 99 before pressure fluid is admitted into the throttle valve through the port 43. Simultaneously the groove 81 is moved in communication with the port 98, permitting thereby the pres-v sure fluid previously admitting into the front end v Yinto the throttle valve groove 81, from Where it Will flow into the sprocket Wheel chamber E39 via the port |24, and from there to the atmosphere through the open side of the chamber. When the throttle valve 15 and its appurtenant handle 18 is rotated sufficiently to cause the compression of the spring 65 by the cam 9| forcing the cap 66 inwardly, the valve shoulder 12 will move avvay from its valve seat as previously explained, admitting thereby pressure fluid from the groove 19 into the groove 69 from where itiwill iiow in-the throttle valve bore 84 via the ports 43 and 94. From the throttle valve 15, the pressure fluid's free to flow through the throttle valve port 9| and groove 92 into the clearance 56 existing around the piston rod 39 via the port 99, from where it is free to be admitted into the rear end of thel feed tube 32. The pressure fluid admitted therein will act on the pair of packing members 35 and 58, affording thereby a fluid tight joint preventing the` pressure fluid to escape from the feed tube, the piston rod 39 being packed by the stung box 55. 'Ihe pressure iluid thus admitted into the rear end of the feed tube 32 will cause the slidable movement of the latter within the guideways 2| and 22 of the support 20 toward the left in'Fig. 3 or away from the work. 'Ihe sprocket wheel |0| being carried by the feed tube will move therewith causing thereby the chain |03 engaging the latter to pull the drilling motor |08 within the guidewaysV |09 of the feed tube 32 in the same direction or away from the work, but at a greater rate of speed than that of the feed tube 32. The other chain H3 being pulled by the drilling motor |08 to which one end is attached, will simply pass `over the sprocket Wheel I4 without affecting the operation of the mechanism.

Referring now to the operation of the fluid controlling valve, assuming that the pressure iluid was admitted into the rear end of the feed tube 32 to move the drilling motor |08 away from the work. In this instance the throttle valve handle i8 would be positioned in a manner whereby the cam 8i would cause the valve head 6| to uncover the groove '10. Should for instance the pressure of the fluid thus admitted into the rear end of the Y feed tube be increased due to some adverse conditions retarding the slidable movement of the drilling motor away from the work, the pressure of the fluid admitted into the valve head 6| through the restricted port 08 will increase proportionally, thus causing the movement of the valve 60 and its appurtenant head 6| to move toward the bottom of the counterbore 59 for partly closing the groove V'|0, reducing thereby the amount of the pressure fluid flowing from the groove 'l0 into the rear end of the feed tube via the groove 99. In this instance, since the amount of the pressure fluid admitted into the feed tube is restricted due to an increase of the pressure of the fluid admitted therein, `it will be understood that the pressure within the feed tube will remain substantially constant for a predetermined position of the throttle Valve handle 18. Should the pressure of the fluid within the feed tube decrease due to Working conditions permitting a freer slidable movement of the drilling motor, the pressure of the fluid within the head 6| of the valve 60 will also decrease, permitting thereby the valve to move toward the plug 59. In this instance the groove l0 is more Vfully uncovered by the head of the valve, thus permitting an increased amount of the pressure fluid to flow into the groove 69, and therefrom into the feed tube 32 for maintaining the pressure of the fluid therein substantially constant. When the throttle valve handle is finally positioned at the extreme end of its rotation in a counterclockwise direction, the portl 86 of the throttle valve is in communication with the port 95, thus admitting pressure iluid into the cylindrical bore 5l, between the valve 68 and the cap 66, for shifting and maintaining the valve 60 in its extreme open position, assuring thereby an unreetrlcted flow of the pressure fluid from the groove 'l0 into the groove 69 and therefrom into the feed tube 32 via the throttle valve 16. When the handle '18 is again rotated in a clockwise direction, the pressure fluid previously admitted into the cylindrical bore via the throttle valve port 36Y and the port 95, is now free to exhaust therefrom through a vent 1| provided through the Vcap 66, permitting thereby the normal operation of the valve 60 responsive to the effort of the compression springs 64 and 65.

When vit is desired to feed Vthe drilling moto toward the work, the throttle'valve from its vermitting thereby the pressure fluid flowing from 1 the'groove 'l0 into the groove 69to be admitted into the front endof thefeed tube 32 via the port 98; bore 96, and tube 91. The pressure fluid admitted therein will act on the pair of packing members 36 to afford a fluid tight joint with theinternal wall of the feed tube 32. Similarly thepressure fluid will act on the plate 4| which is integral with the feed tube 32 to cause the vslidable movement of the latter within the guideways 2|A and 22 of the supportY 20 in a rightwardk direction or Ytoward the Work. The sprocket wheel ||4 carried-bythe feed tube 32, will cause `the chain ||3 to impart slidable movement tothedrilling motor |08 within the guideways |09 of the Vfeed tube 32 in the same direction but at a greater rateV of speed than that of the feed tube 32. During this slidable movement of the drilling motor, the chain |03 engaging the sprocket wheel |0| will simply pass thereover without affecting the operation of the mechanism.

In this instance, theoperation ofthe pressure controlling valve 68 is identical to that previously described, consequently no further explanation is thought necessary other than pointing out that the pressure controlling Valve being located ahead of the throttle valve '|6, is capable of controlling the pressure of the fluid within both ends of the feed tube 32 or irrespective of the direction of the slidable movement thereof.

When the throttle valve is positioned for adinitting pressure fluid into the front end of the. feed tube 32, the pressure fluid previously admitted `into the rear end of the feed tube-is free to exhaust therefrom through the clearance 56 existing around the piston rod 39, the port99 into the throttle groove 90, from where itV will flow into the groovev 8l via the slot 93. groove 81 being constantly in communication with the exhaust port |24, theexhausting iluid is'free to flow therethrough into the chamberk ||00, and therefrom to the atmosphere viathe open side of the chamber through which the chain 03 passes. When the throttle Vvalve handle is located at the leXtremeV end of its rotation in a clockwise direction, the port 85 is in communication with theI portfor admitting pressure Yfluid between the valve 60V and the capv 66 as previously explained.. Y K

The feed tube 32 together with the drilling motor |08 may be locked against slidabler movement relative to the support 20 byrotating .the

the drilling motor is preventedV to move relatively to the feed tube by the chains |03 and H3 uniting the former to the latter. p-

'I'he tension of the two chains |03 and I3 mayI be varied by rotatingthe nut |06, thusroausing.

the slidable movement of the bolt |84 through the apertured lug |05, and thereby varying the ten-1 sion of the chains |03 and ||2.

Although the foregoing Vdescription is necessarily of a detailed character, in order topcompletely set forth the invention, it is to be understood that the specic terminology is rnot in- Thefof

accessi tended to be restrictive or confining and it is to be further understood that variousrearrangements of parts and modilcationof structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

I claim:

1. In a rock drill, a support, a tube slidably guided thereon, a drilling motor slidably guided on said tube, a feeding mechanism for said drilling motor including said slidable tube, a stationary element within the latter, means for effecting the slidable movement of said tube relative to said element, and means receiving motion from the slidable movement of said tube for effecting the slidable movement of said drilling motor relative to said tube.

2. In a feeding mechanism for a rock drill, a stationary member, a slidable element carried by said member, a drilling motor carried by said element in slidable engagement therewith above said member, and means actuated by said element for imparting slidable movement to said drilling motor relative to said element.

3. In a feeding mechanism for a rock drill, a stationary member, a feeding element carried by said member normally extending beyond the ends of the latter, a drilling motor carried by y said element, means for effecting relative motion between said member and elernlent, and means deriving motion from said relative motion for imparting feeding motion to said drilling motor relative to said element.

4. In a rock drill, a stationary elongated support, a fluid actuated feeding element slidably guided on and carried by said support, a drilling motor slidably guided on and carried by said element, and means deriving motion from the slidable movement of said element for imparting feeding motion to said drilling motor in a manner whereby the relative rate of speed between the interengaging guiding surfaces of said element and support is equal to the relative rate of speed between the interengaging guiding surfaces of said element and motor.

5. In a rock drill, a stationary elongated support, a fluid actuated feeding element slidably guided on and carried by said support, a drilling motor carried by said element, interengaging walls on said motor and element for slidably guiding the former relative to the latter, and means deriving motion from the slidable movement of said element for imparting feeding motion to said drilling motor in a manner whereby the relative rate of speed between the interengaging walls aforesaid is less than the rate of speed of the motor relative to the support.

6. In a rock drill, a support, a drilling motor slidable relatively thereto, a reversible feeding mechanism for said motor including an element slidably guided on and carried by said support, said element carrying said motor in relative slidable engagement therewith, and means for transmitting the slidable movement of said element to said drilling motor in a manner whereby the speed of the latter is substantially multiplied.`

7. In a rock drill, a support, a feeding element slidably guided thereon, a drilling motor slidably guided on said element, and a feeding mechanism for said drilling motor including said feeding element, a stationary piston member within the latter, and a speed multiplying device including a flexible member connecting said support to said drilling motor and associated with rotatable memberscarried by said element for rotation one in a horizontal and the other in a vertical'plane relative to said support.

8. In a drilling apparatus, the combination with a drilling motorhaving a fluid actuated feeding mechanism associated therewith for feeding the latter toward or away from the work, and means including a valve for controlling the pressure of the fluid actuating said feeding mechanism irrespective of the direction of feed imparted to said drilling motor, said valve having differential opposed areas subjected to pressure conditions within said mechanism forautomatically actuating the valve.

9. In a feeding device for a rock drill, the combination with a stationary support, of a cylinder element carriedby. said support, a drilling motor slidably guided on said cylinder element, a motivev fluid actuated feeding mechanism for said drilling motor including a piston element within said cylinder element, means for admitting motive fluid to said elements for causing the slidable movement of one relatively to the other in either direction, means receiving motion froml said slidable element for imparting feeding motion to said drilling motorY relative to said slidable element, and means for maintaining substantially constant the pressure of the motive fluid actuatingy said slidable element irrespective 'of the speed and the direction of travel of the latter, t

l0. In 'a drilling apparatus, the combinationv with a drilling motor having a fluid actuated feeding mechanism associated therewith for feeding the latter toward or away from the work, said feeding mechanism including a piston element and a cylinder element one slidable relatively to the other in either direction, passages for admitting motive fluid to said slidable element for effecting its slidable movement, means for transmitting said slidable movement to said drilling motor, means including a valve for maintaining substantially constant the pressure of the motive fluid actuating said element irrespective of the direction of travel of the latter, means resiliently supporting said valve, and actuating areas on said valve subjected to pressure conditions Within said feeding mechanism for actuating the valve. Y

11. In a drilling apparatus, the combination with a rock drill, of a motive fluid actuated feeding mechanism associated with the drill for imparting feeding motion thereto in two directions, and means including a valve automatically operated due to a variation of the pressure of the motive fluid actuating said feeding mechanism for maintaining said pressure substantially constant irrespective of the direction of said feeding motion.

12. In a drilling apparatus, the combination with a drilling motor, of a power actuated feeding mechanism associated therewith for imparting feeding motion thereto in two directions, means movable in different positions for varying the power of said feeding mechanism, and means automatically operated to maintain said power substantially constant for each position of said first mentioned means irrespective of the speed and direction of the feeding movement imparted to said drilling motor. v

13. In a drilling apparatus, the combination with a drilling motor, of a fluid actuated feeding mechanism associated therewith for imparting feeding motion thereto, passages for admitting pressure fluid in either end of said feeding mechanism, a primary valve movable in more or less complete open position for controlling the amountV of the pressure fluid adapted to be admitted through either of saidpassages, a secondary valve controlling Vsaid passages movable in open position with either one thereof before said primary valve is moved in an open position, an adjustable compression spring acting on said secondary valve normally effecting the opening thereof relative to said passages, common means for operating said primary valve and adjusting the compression of said spring, and means assuring the complete open position of said primary valve during a pre-determined position of said secondary valve. y

14. In a drilling apparatus, the combination with a rock drill, `of a reversible pressure fluid actuated feeding motor for said rock drill, means including a duality of passages for admitting fluid to and exhausting fluid from said feeding motor to actuate the latter, a throttle valve controlling said passages and adjustable for eilecting feed in either direction, an automatic valve subjected to pressure conditions within said feeding motor for controlling the supply of fluid through either of said passages for automatically regulating the feeding pressure within said motor, a load acting on said automatic Valve adjustable for changing the feeding pressure within said motor, and a single element for operating said throttle valve and adjusting the load acting on said automatic valve.

. 1 5. In a drilling apparatus, the combination with a drilling motor, of a lpressure iluid actuatedfeeding mechanism associated with the motor for feedingV it in two directions, a throttle valve for controlling the direction'of travel of said motor, a spring loaded valve subjected to pressure condition within said feeding mechanism for maintaining said pressure substantial- 1y constant irrespective of the direction of travel of said motor, and a single element manuallyoperable for actuating said throttle valve and for varying the load of the spring acting on said valve Vfor changing the pressure-of the fluid actuating said feeding mechanism.

16.`In a drilling apparatus, the combination with a rock drill, of a reversible pressure fluid actuated feeding motor for said rock drill, means including passages for admitting and exhausting pressure fluid to and from said motor for actuating the same, a primary valve normally actuated by virtue of pressure conditions within said motor for automatically controlling the feeding pressure of the motor irrespective of the direction of movement of the latter, a manually operated secondary valve controlling said passages for effecting forward or rearward movement of said motor, and means controlled by said secondary valve for rendering said primary` Valve inoperative.

Y JOHN C. CURTIS. 

